We would like to use our ultra-low temperature XMCD apparatus to examine the magnetic/electronic properties of complex biological samples. Although this technique is relatively new, we have already obtained data which shows the strong feasibility of the experiments. With our apparatus, we can reach fields as high as 6 Tesla, with a temperature of around .5K, or we can use our new rapid-sweep magnet which can go as high as 2 Tesla, with less than 130 mK. Using the beamline 5 EPU, we have obtained excellent results and would like to further that work. Since many complex metalloproteins are involved in important biological redox reactions, knowledge of their magnetic and electronic properties is important for a complete understanding of the enzymatic function.